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Submitted on: 03 January 2014.
Revised on: 04 March 2014.
Accepted on: 16 April 2014.
___________________Global Sustainability---CAMBRIDGE UNIV PRESS
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Submitted on: 19 October 2011.
Revised on: 24 January 2012.
Accepted on: 09 February 2012.
___________________Global Sustainability---CAMBRIDGE UNIV PRESS